Editors' Choice: Aero Road Bikes

Cheating the Wind

8 / 8

Our Testing Protocol. —Matt Phillips

—In the tunnel, everything, no matter now small, makes a difference. Even details like saddle height and the thickness of the bar tape can alter the numbers. Cervélo’s David Kennedy says he has found that even the direction the bar tape is wrapped can affect results. We controlled every variable that we could, but our data may not match that collected in other tests.

—We tested each bike two ways: with the wheels you’ll get when buying the bike, and also with a control set of wheels—Zipp Firecrest 404 tubulars shod with Vittoria EVO CX 23mm tires. Every bike (all were size 54cm) was tested with a Fi’zi:k Arione saddle set to the same height and setback. We also cut steerer tubes to the same height and installed the stem at the same angle. While testing the frames with matching components may have yielded different results, we believe that this method let us better test the bikes you will buy.

—We tested without bottles or cages. While these items definitely affect overall drag numbers, we chose to test without them in order to eliminate a large variable.

—Some manufacturers claim their aerodynamics are optimized to work with a rider, but we tested the bikes without a rider or dummy. A human isn’t consistent enough to maintain the same position on each of six bikes; even a subtle shift in the saddle or head tilt could skew the data.

—We tested the bikes with a straight-on headwind, and with the wind coming from five-degree increments up to 20 degrees on both sides of the bikes. In the real world, the effective wind angle is a combination of both the speed and direction of your travel, and the wind’s speed and direction. If you’re traveling at 20 mph and there is a 20-mph wind blowing from 20 degrees, the effective wind angle is 10 degrees. If a rider is traveling at 20 mph and there is a 5 mph wind blowing from 30 degrees, the effective wind angle is TK. Engineers disagree on the question of which is the average effective wind angle that most riders experience, but most believe that it’s between five and 15 degrees.